Anyone else experienced this bug?
Can't say that I have (I'll try make an attempt to let it crash but so far was out of luck -> GTK2).
In case it is reproducible, you could opt to create debug build of the IDE, catch the exception log and create an issue on the bugtracker with al gathered information. Note that KDE/Wayland is far from stable (despite what the buzz on the internet is telling). Advisable is to switch to xwayland (most distributions based on KDE/Wayland have some form of a quick toggle to switch to X). My experience with wayland and Lazarus is very negative because it is riddled with annoying bugs that unexpectedly pops up and makes it impossible to use in a serious work environment.